Pith
Protection Zone - Also now being referred to as a "Pith Plug". A sheath about the trunk pith separates the
trunk pith from the branch pith. Also, at the base of the branch
pith the cells appear more compact. This zone is called the pith
protection zone. The cells have thicker walls in this zone, and the
cells contain a higher amount of phenols. The branch pith and the
trunk pith are not connected in a conducting way. Arrow points to the
pith protection zone in a Norway maple.